Tire with low zone comprising a concentration of cords

ABSTRACT

A tire comprising at least one reinforcement structure of the carcass type anchored on either side of the tire in a bead, the base of which bead is intended to be mounted on a rim seat, the reinforcement structure extending circumferentially from the bead towards the sidewall, at least one arrangement of main cords along a substantially circumferential path being arranged substantially adjacent to the structure, the arrangement of the cords of the at least one arrangement being such that the number of main cords arranged on the axially inner side relative to the structure is greater than the number of main cords arranged on the axially outer side relative to the structure.

CROSS REFERENCE TO RELATED APPLICATIONS

This is a continuation of international application PCT/EP00/11190 filedNov. 13, 2000, published in French on May 25, 2001 as internationalpublication WO 01/36219 A1.

BACKGROUND OF THE INVENTION

1. Technical Field of the Invention

The present invention relates to tires. More particularly, it relates tothe arrangement of the reinforcement cords in the sidewalls and in thebeads. It also relates to the anchoring of the carcass cords in the beadand the reinforcements of different portions of the bead or thesidewall.

2. The Related Art

The carcass reinforcement of tires is at present formed by one or moreplies, most frequently radial plies, which are turned up about one ormore bead wires arranged in the beads. The beads constitute the meanswhich makes it possible to fix the tire on the rim. The rigidity of thebead thus formed is very great.

For some specific applications, in which the tire may, for example, besubjected to greater loads or to more violent impacts, etc., it mayprove desirable to be able to refine some characteristics such asrigidity, impact strength, etc. Furthermore, in order to facilitateautomation of certain steps of the tire manufacturing process, it mayprove advantageous to revise the nature and/or the arrangement of someof the constituent elements.

In the current art, it is quite difficult to ensure modulation of thecharacteristics of the sidewall and/or of the bead. The sidewall musthave great flexibility, and the bead, in contrast, must have greatrigidity. Furthermore, the reinforcements which are arranged in thispart of the tire always inevitably have a discontinuity: at the level ofthe radially upper end of the carcass upturn, there is passage withouttransition into a zone devoid of the carcass upturn, which zone istherefore inevitably less rigid.

As a reminder, “radially upwards” or “radially upper” means towards thelargest radii. In the case of radial carcasses, other principles ofdesign are already known which make it possible to avoid upturns about abead wire. By way of example, reference may be made to U.S. Pat. No.3,072,171, in which it was proposed to dispense with the upturn of thecarcass plies and to arrange cords oriented circumferentially. In thisknown structure, however, it is difficult to ensure sufficiently stronganchoring of the carcass cords to the cords which are orientedcircumferentially, which means that this proposal has never been appliedin practice.

Furthermore, there is known from EP 0 582 196 a method of arranging thereinforcements of the carcass ply in the beads, by arrangingcircumferential filaments adjacent to the reinforcements, the wholebeing embedded in a connecting rubber of high elasticity modulus.Several arrangements are proposed in this document. In all cases, thereare more axially inner reinforcement cords relative to the reinforcementstructure than there are axially outer cords.

SUMMARY OF THE INVENTION

A first object of the invention is to overcome the foregoingdisadvantages of the prior art.

Another object of the invention is to propose a type of arrangement ofthe various constituent elements of a tire in order to be able to refinecertain characteristics such as rigidity, impact resistance, etc.

Another object of the invention is to propose a tire reinforcementstructure which lends itself readily to mechanised manufacture.

Another object of the invention is to propose a tire reinforcementstructure which takes into account the different mechanical stressesoccurring in the different zones of the beads during operation, inparticular at rated pressure.

Another object of the invention is to propose an arrangement of thebottom zone of the tire which provides effective, durable anchoring ofthe reinforcement structure in the beads of the tire.

The foregoing objects are attained in accordance with the invention byproviding a tire comprising at least one reinforcement structure of thecarcass type anchored on either side of the tire in a bead, the base ofwhich is intended to be mounted on a rim seat, each bead being extendedradially towards the outside by a sidewall and comprising an axialbearing zone extending substantially between the base of the bead and aradial position of such bead substantially corresponding to the positionof the radial edge of the hook of a rim for which the tire is adapted,the sidewalls radially towards the outside joining a tread, on thecircumference of the tire the reinforcement structure extending from anend portion of the structure, arranged in the bead, towards thesidewall, at least one arrangement of main cords along a substantiallycircumferential path being arranged substantially adjacent to the endportion so as to form an anchoring zone, the arrangement of the cords ofthe arrangements being such that the number of main cords arranged onthe axially inner side relative to the structure is greater than thenumber of main cords arranged on the axially outer side relative to thestructure, the main cords extending substantially radially to the insideof the axial bearing zone.

The comparisons are advantageously effected in the zone of the bead,namely, for example, from the seat to a zone located at the upper, orradially outer, level of the portion adapted to the rim hook. The cordslocated radially to the outside of this portion are not considered. Themain cords are advantageously arranged such that their radial positiondoes not extend beyond the outermost radial position of the hook of arim on which the tire is to be mounted, so as to improve thecontribution of the main cords to the endurance of the bottom zone.

Such an arrangement makes it possible to optimize the mechanicalbehavior of the bottom zone of the tire, in particular at the level ofthe bead. In fact, the stresses which act on either side of thereinforcement structure are generally not symmetrical. The presentinvention makes it possible better to make allowance for theseconditions. Thus, for example, the main cords are advantageously greaterin number in a zone liable to be subjected to great tensile stresses atrated pressure and during travel, and advantageously fewer in number, oreven absent, in a zone liable to be subjected to great compressivestresses. Such an arrangement may contribute to reducing the tendency ofthe bead to overturn.

It has been noted that the stresses which act on either side of thereinforcement structure are not symmetrical. According to the invention,the bead is designed so as to optimize the behavior of the bottom zoneof the tire, according to these different stresses.

In fact, the compressive stresses are well supported and welldistributed in a homogenous zone. As for the tensile forces, they aredampened by the presence of the cords, which thus contributes tooptimizing the mechanical behavior of a highly stressed zone.

Preferably, it is desired to counter the effect of rotation, in order topromote the holding in place of the bead.

The main cords are the cords which participate in the function ofanchoring the carcass-type reinforcement structure in the bead and/or ofclamping the bead, so that, without these cords, the function ofanchoring and/or clamping could not be guaranteed, or even assured.

Thus, the main cords are advantageously of the metallic type. The maincords advantageously have a high elastic modulus and are advantageouslycontinuous. These cords preferably have a high initial modulus.

The secondary cords are the cords which do not participate substantiallyor in a determining manner in the function of anchoring the carcass-typereinforcement structure in the bead and/or of clamping the bead, sothat, without these cords, the function of anchoring and/or of clampingcould not be seriously affected, or would continue to be ensured by themain cords.

Thus, the secondary cords are advantageously of the textile type. Thesecondary cords advantageously have a lower elastic modulus than that ofthe main cords.

According to this first aspect of the invention, the secondary cords arenot included in the comparison of the numbers of cords.

According to an advantageous variant, all the arrangements of main cordsare on the axially inner side relative to the structure.

According to another advantageous variant, the tire also comprises atleast one arrangement of secondary cords which are arranged axially tothe outside relative to said reinforcement structure.

The secondary cords contribute to optimizing the lateral rigidity of thetire, in particular above the rim hook, with the possibility ofmodulating the arrangements according to the specific characteristicsfor specific zones. For example, provision may be made for a singlealignment of secondary cords on a portion of the bottom zone, and adouble or even triple alignment on another portion where it is desiredto increase the rigidity or to provide protection against potentialimpacts which might affect the integrity of the tire. Furthermore, thesecondary cords may be provided so as to provide protection against wearat the interface with the rim.

The secondary cords are advantageously non-metallic, and preferably ofthe textile type.

The carcass-type reinforcement structure is preferably a single-cordstructure.

Preferably, the cords and the portion of the structure in the immediatevicinity are embedded in a rubber mix of high modulus, for example amodulus greater than 25 MPa and preferably greater than 40 MPa.

According to an advantageous variant, the reinforcement structurecomprises, at the level of the beads, two structure portions, withinterposition of an arrangement of primary and/or secondary cordsbetween the adjacent portions.

According to another advantageous variant, the reinforcement structurecomprises, at the level of the beads, three or more structure portions,with interposition of an arrangement of primary and/or secondary cordsbetween adjacent portions.

Advantageously, a zone of rubber of high modulus is provided betweenadjacent portions of the structure.

Advantageously, the secondary cords are arranged so as to be in contactwith at least one rubber mix of high modulus. It is also possible toprovide for the arrangement to be surrounded on one side by a first mixand on the other side by a second mix.

According to an advantageous variant, that zone of the bead which islocated axially to the inside is formed at least in part of a rubber mixof high modulus. The presence in this zone of a material of this typecontributes to ensuring optimum behavior of the bottom zone of the tire.In fact, such a material provides better resistance to tensile stresses.

According to an advantageous variant, that zone of the bead which islocated axially to the outside is formed at least in part of a rubbermix of low modulus. The presence in this zone of a material of this typecontributes to ensuring optimum behavior of the bottom zone of the tire.

According to another aspect of the invention, there is provided a tirecomprising at least one reinforcement structure anchored on either sideof the tire in a bead, the base of which is intended to be mounted on arim seat, each bead being extended radially towards the outside by asidewall and comprising a zone of axial bearing extending substantiallybetween the base of the bead and a radial position of the beadsubstantially corresponding to the position of the radial edge of thehook of a rim for which the tire is adapted, the sidewalls radiallytowards the outside joining a tread, on the circumference of the tirethe reinforcement structure extending from an end portion of thestructure, arranged in the bead, towards the sidewall, at least in theend portion the structure being axially separated into at least twoportions, at least one arrangement of main cords along a substantiallycircumferential path being arranged substantially adjacent to at leastone of the portions of the structure so as to form an anchoring zone,the arrangement of the cords of the arrangements being such that thesurface density of main cords which are arranged on the axially innerside relative to the structure is greater than the surface density ofmain cords arranged on the axially outer side relative to the structure,the main cords extending substantially radially to the inside of saidzone of axial bearing.

In this context, where the reinforcement structure, at least at thelevel of the beads, is divided into several parts, the possiblearrangements arranged between structure portions are not taken intoaccount. Only the arrangements axially to the inside and axially to theoutside of the structure are compared: the structure portions, with thepossible intra-structure arrangements, are considered as a whole.Therefore, only the arrangements of main cords located on either side ofthe extreme structure portions are compared.

According to an advantageous variant, the reinforcement structurecomprises, at the level of the bead, two structure portions, with theinterposition of at least one arrangement of main and/or secondary cordsbetween the adjacent portions.

According to another advantageous variant, the reinforcement structurecomprises, at the level of the bead, three or more structure portions,with the interposition of at least one arrangement of main and/orsecondary cords between adjacent portions.

Advantageously, a zone of rubber of high modulus is provided betweenadjacent portions of the structure.

According to an advantageous variant, all of the arrangements of maincords are on the axially inner side relative to said structure. Hereagain, this excludes the possible intra-structure arrangements.

According to another advantageous variant, the tire also comprises atleast one arrangement of secondary cords which are arranged axially tothe outside relative to the reinforcement structure.

The secondary cords are advantageously non-metallic, and preferably ofthe textile type.

The main cords advantageously have a high elastic modulus.

Advantageously, at least one portion of the main cords and the structureportion in the immediate vicinity of the main cords are embedded in arubber mix of high modulus, namely, for example, a modulus greater than25 MPa and preferably greater than 40 MPa.

Advantageously, the secondary cords are arranged so as to be in contactwith at least one rubber mix of high modulus. It is also possible toprovide for the arrangement to be surrounded on one side by a first mixand on the other side by a second mix.

“Secondary cord” is understood to mean a cord, the modulus of which isless than 20,000 daN/mm² and preferably less than 15,000 daN/mm².Advantageously, cords of textile type are used, such as cords based onaramid, aromatic polyester, or alternatively other types of cords havinglower moduli, such as cords based on PET, rayon, etc.

Preferably, the circumferentially oriented cords are not in directcontact with the radially oriented cords. Advantageously, for tireswhich are subject to high stresses, in order to ensure good transmissionof the forces between the portions of cords of the reinforcementstructure and the circumferentially oriented cords, there is interposeda rubber of high elasticity modulus, that is to say, a rubber mix havinga Shore A hardness greater than 70, between the circumferentiallyoriented cords and the adjacent alignment of carcass cords.

According to another aspect of the invention, there is provided a tirecomprising at least one reinforcement structure of the carcass typeanchored on either side of the tire in a bead, the base of which isintended to be mounted on a rim seat, each bead being extended radiallytowards the outside by a sidewall, the sidewalls radially towards theoutside joining a tread, on the circumference of the tire thereinforcement structure extending from an end portion of the structure,arranged in the bead, towards the sidewall, at least one arrangement ofcords along a substantially circumferential path being arrangedsubstantially adjacent to the end portion, each cord arranged on theaxially inner side relative to the structure having a Young's modulusE_(I) and a surface S_(I) and each cord arranged on the axially outerside relative to the structure having a Young's modulus E_(e) and asurface S_(e), the arrangement of the cords of the arrangements beingsuch that Σ(E_(I)×S_(I))_(int)>Σ(E_(e)×S_(e))_(ext).

According to this embodiment, the resultant internal rigidity is greaterthan the resultant external rigidity.

It should be noted that in the case of a multi-filament cable or a cablehaving multiple cords, the section considered is the effective section.The free or empty spaces between the cords are not considered.

Advantageously, the total of the products E×S is considered solely inthe zone of the beads of the tire. Thus, if, for example, protectivecords, often of textile type, are located in a portion of the sidewalland/or the crown, these cords will not be considered in the equation.

According to an advantageous variant, the value of S_(e) is zero.

According to an advantageous variant of the invention, Σ(E_(I)×S_(I))_(int)/Σ (E_(e)×S_(e))_(ext) >1.

According to another advantageous variant of the invention,Σ(E_(I)×S_(I))_(int)/Σ(E_(e)×S_(e))_(ext) >1.5.

According to another advantageous variant of the invention,Σ(E_(I)×S_(I))_(int)/Σ(E_(e)×S_(e))_(ext) >10.

It is known that in the current art the carcass ply or plies is/areturned up about a bead wire. The bead wire then performs the function ofanchoring the carcass, that is to say, takes up the tension whichdevelops in the carcass cords under the action of the inflationpressure. In the configurations described in the present application,the function of anchoring the reinforcement structure of the carcasstype is also ensured.

It is also known, still in the prior art, that the same bead wirefurthermore performs a function of clamping the bead on its rim. In theconfigurations described in the present application, the clampingfunction is also ensured, in particular by the windings ofcircumferential cords which are closest to the seat.

It will be understood that the invention can be used by adding otherelements to the bead or to the bottom zone of the tire in general, assome variants will illustrate. Likewise, the invention can be used bymultiplying the reinforcement structures of the same type, or even byadding another type of reinforcement structure.

In the present specification, the term “cord” very generally designatesboth monofilaments and multifilaments, or assemblies such as cables,plied yams or alternatively any equivalent type of assembly, and thiswhatever the material and the treatment of these cords, for examplesurface treatment or coating or pre-sizing in order to promote adhesionto the rubber.

A reinforcement or reinforcing structure of the carcass type will besaid to be radial when its cords are arranged at 90°, but also,according to the terminology in use, at an angle close to 90°.

In the present application, the term “main cord” indicates a cord ofhigh modulus, namely for example 20,000 daN/mm² or more. Such a modulusmay be achieved, for example, by a metallic-type cord, such as a steelwire.

BRIEF DESCRIPTION OF THE DRAWINGS

For a better understanding of the invention, reference may be made tothe following description of exemplary embodiments thereof, taken inconjunction with the accompanying drawings, in which:

FIG. 1 is a radial section essentially showing a sidewall and a bead ofa first embodiment of a tire according to the invention;

FIG. 2 is a radial section essentially showing a sidewall and a bead ofa variant of the embodiment of FIG. 1;

FIG. 3 is a radial section essentially showing a sidewall and a bead ofanother variant of the embodiment of FIG. 1;

FIG. 4 is a radial section essentially showing a sidewall and a bead ofa second embodiment of a tire according to the invention;

FIG. 5 is a radial section essentially showing a sidewall and a bead ofanother embodiment of a tire according to the invention;

FIG. 6 is a radial section essentially showing a sidewall and a bead ofa variant of the embodiment of FIG. 5;

FIG. 7 is a radial section essentially showing a sidewall and a bead ofa variant of the embodiment of FIG. 6;

FIG. 8 is a radial section essentially showing a sidewall and a bead ofanother variant of the embodiment of FIG. 6;

FIG. 9 is a radial section essentially showing a sidewall and a bead ofanother variant of the embodiment of FIG. 6;

FIG. 10 is a radial section essentially showing a sidewall and a bead ofanother variant of the embodiment of FIG. 6;

FIG. 11 is a radial section essentially showing a sidewall and a bead ofanother embodiment of a tire according to the invention;

FIG. 12 is a radial section essentially showing a sidewall and a bead ofa variant of the embodiment of FIG. 11, comprising primary cords ofdifferent diameters; and

FIG. 13 is a radial section essentially showing half a tire of anothervariant of the embodiment of FIG. 5.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

FIG. 1 shows the bottom zone, in particular the bead 1, of a firstembodiment of the tire according to the invention. The bead 1 comprisesan axially pouter portion 2 which is provided and shaped so as to beplaced against the flange of a standard rim. The upper portion, orradially outer portion, of the portion 2 forms a portion 65 adapted tothe rim hook. This portion is frequently curved axially towards theoutside, as illustrated in FIGS. 1 and 2. The portion 2 ends radiallyand axially towards the inside in a bead seat 4 which is adapted to beplaced against a rim seat. The bead also comprises an axially innerportion 3, which extends substantially radially from the seat 4 towardsthe sidewall 6.

The tire also comprises a reinforcement or reinforcing structure 10 ofthe carcass type provided with reinforcements which are advantageouslyshaped in a substantially radial arrangement. This structure may bearranged continuously from one bead to the other, passing through thesidewalls and the crown of the tire. Alternatively, it may comprise twoor more parts, arranged for example along the sidewalls, withoutcovering the entire crown.

In order to position the reinforcement cords as accurately as possible,it is very advantageous to build the tire on a rigid support, forexample a rigid core which imposes the shape of its inner cavity. Thereare applied to this core, in the order required by the finalarchitecture, all the constituents of the tire, which are arrangeddirectly in their final position, without the profile of the tire havingto be modified during building.

Circumferential cords 21, preferably arranged in the form of stacks 22,form an arrangement of main cords 20, which is provided in each of thebeads. These cords are preferably metallic, and possibly brass-coated.In each stack 22, the cords are advantageously substantially concentricand superposed.

In order to ensure perfect anchoring of the reinforcement structure 10,a stratified composite bead 1 is produced. Within the bead 1, betweenthe cord alignments of the reinforcement structure 10, there arearranged circumferentially oriented cords. These are arranged in a stackas in the drawings, or in a plurality of adjacent stacks, or in packets,or in any suitable arrangement, depending on the type of tire and/or thedesired characteristics.

The radially inner end portions of the reinforcement structure 10cooperate with the beads. There is thus effected anchoring of theseinner end portions in the beads so as to ensure the integrity of thetire. In order to promote such anchoring, the space between thecircumferential cords and the reinforcement structure is occupied by aconnecting rubber mix. It is also possible to provide for the use of aplurality of mixes having different characteristics, defining aplurality of zones, the combinations of mixes and the resultantarrangements being virtually unlimited. However, it is advantageous toprovide for the presence of a mix of high elasticity modulus in the zoneof intersection between the arrangement of cords and the reinforcementstructure. By way of non-limitative example, the elasticity modulus ofsuch a mix may reach or even exceed 25 MPa, and even in some cases reachor even exceed 40 MPa.

The arrangements of cords may be arranged and manufactured in severalways. For example, a stack 22 may advantageously be formed of a singlecord wound (substantially at zero degrees) in a spiral over severalturns, preferably from the smallest diameter towards the largestdiameter. A stack may also be formed of a plurality of concentric cordslaid one within another, so that rings of gradually increasing diameterare superposed. It is not necessary to add a rubber mix to ensure theimpregnation of the reinforcement cord, or circumferential windings ofcord.

According to the invention, the main cords 21 are of priority arrangedon the axially inner side of the bead. Thus, in the example of FIG. 1,the axially inner portion comprises an arrangement of main cords formedof two stacks 23 of juxtaposed cords. They are advantageously arrangedin the immediate vicinity of the reinforcement structure 10. Thestructure illustrated in FIG. 1 is particularly simplified and simple toproduce. The forces of the reinforcement structure 10 are transmitted tothe zero-degree windings 21 by means of a mix having suitablecharacteristics.

This embodiment is well-suited in particular for tires of thepassenger-vehicle type in general, or alternatively for tires having ahigh speed index of the passenger-car or two-wheeler type.

FIG. 2 illustrates a variant of the embodiment of FIG. 1, furthermorecomprising an arrangement 30 of secondary cords 31, preferably oftextile type. In this example, the arrangement of secondary cords isarranged in the axially outer portion 2 of the bead, along thereinforcement structure 10. The arrangement may advantageously be formedof a single cord wound (substantially at zero degrees) in a spiral,preferably from the smallest diameter towards the largest diameter. Astack may also be formed of a plurality of concentric cords laid onewithin another. The arrangement 30 of secondary cords 31 may be extendedsubstantially radially along the sidewall or a portion thereof. Withoutdeparting from the scope of the invention, one or more arrangements ofsecondary cords could be provided within other zones of the tire.

The number of windings, the radial spacing and the radial position ofthe arrangements may vary in an infinite number of possibilities. Thesecharacteristics are defined according to the qualities desired at thebottom zone of the tire, such as rigidity, wear resistance, endurance,etc.

In this same figure, a rim 90 matched to the tire so as to permitmounting of the assembly is also illustrated. The point 91 which is theoutermost point of the hook 92 of this rim is advantageously used as adelimitation for the limiting radial position of the main cords 21 ofthe anchoring zone. It can thus be seen that the main cords 21 arearranged radially internally to the corresponding line 100.

FIG. 3 illustrates another variant of the embodiment of FIG. 1, whichdiffers slightly from that shown in FIG. 2. For example, the arrangement30 of the secondary cords 31 extends substantially radially from thebase of the reinforcement structure 10. The arrangements 20 of maincords 21 are substantially similar and parallel, and the stacks 22 areof the same height.

FIG. 4 shows a second embodiment of the invention in which arrangements20 of main cords 21, advantageously of the cabled or unitary cord type,are provided on either side of the reinforcement structure 10. However,the number of main cords 21 arranged in the axially inner portion 3 isgreater than the number of main cords 21 arranged in the axially outerportion 2.

In the different examples shown, the axially inner portion 3 and theaxially outer portion 2 are advantageously defined by the carcass-typestructure 10.

Advantageously, the number of main cords 21 arranged in the axiallyinner portion 3 is at least 1.5 times greater, and preferably two ormore times greater, than the number of main cords 21 arranged in theaxially outer portion 2.

In the example illustrated in FIG. 4, the number of main cords 21arranged in the axially inner portion 3 is more than two times greaterthan the number of main cords 21 arranged in the axially outer portion2.

Furthermore, in the example of FIG. 4, the arrangements 20 of cords 21and the substantially adjacent portion of the reinforcement structure 10are advantageously arranged in a zone of mix of high modulus 40. Such azone promotes anchoring in the bead of the reinforcement structure. Thisexample is well-suited in particular for a tire for a van or lighttruck, for which good rigidity in the bottom zone is desired.

FIG. 5 shows an example of another embodiment of the tire according tothe invention. This embodiment is distinguished from the previous onemainly by the fact that the reinforcement structure 10 is double atleast at the level of the bottom zone of the tire. Such a configurationinvolves two main families of tires, namely the one comprising tworeinforcement structures and the one comprising a single reinforcementstructure, but a portion of the latter being doubled, for example in thebottom zone of the tire. Usually, but not obligatorily, one or morestacks 22 of main or secondary cords are found between the portions ofreinforcement structure 10.

Within the scope of the present invention, when the respective numbersof cords on either side of the reinforcement structure are compared, thereinforcement structure is considered as a whole, such that any stacksof cords present between portions of reinforcement structure areassimilated into the structure and therefore do not form part of thecomparison of the numbers of cords.

In the example of FIG. 5, the number of main cords 21 arranged in theaxially inner portion 3 is greater than the number of main cords 21arranged in the axially outer portion 2. In fact, there is a stack 22 ofseven cords in the inner portion, while there is no cord in the outerportion 2.

FIG. 13 illustrates a variant of the embodiment shown in FIG. 5comprising only one stack 22 in the central portion.

FIG. 6 shows a variant of the embodiment of FIG. 5, comprising anarrangement 30 of secondary cords 31 which is arranged in the outerportion 2 of the bead and extends even radially externally beyond thebead. This arrangement contributes to the transverse rigidity of thetire. The cords are advantageously made of aramid, hybrid, PET or PEN.As a variant, part or all of the main cords 20 which are arrangedbetween the portions of reinforcement structure 10 could be replaced bysecondary cords, for example textile ones. This example is well-suitedin particular to tires of the passenger-car, van or light-truck andtwo-wheeler types.

FIGS. 7 and 8 illustrate variants of the example of FIG. 6. In FIG. 7,for example, a single stack 22 of main cords is located between the twostructure portions. Alternatively, an arrangement 30 of secondary cords31 comprising two stacks side by side is shown in FIG. 8. Thearrangements of secondary cords 31, preferably of the textile type,provide greater lateral and longitudinal rigidity. The stacks of cords31 of these arrangements 30 extend substantially radially from the beadto the sidewall, beyond the rim hook 5.

FIGS. 9 and 10 illustrate other variants of the example of FIG. 6. Thevariant of FIG. 9 comprises a zone of rubber mix of high modulus 40 aarranged on at least one portion of the path of the two portions ofreinforcement structure 10, i.e., between these two portions. In theexample illustrated, the zone in question does not cover the stacks 22of cords which are arranged between the portions of the structure 10.According to another variant (not shown), the zone also covers thesestacks 22 of cords. The presence of this high-modulus zone contributesto increasing the rigidity of the bottom zone of the tire.

This mix 40 a is advantageously arranged so as to be in direct contactwith the adjacent portions of the reinforcement structure 10. In thetraditional configurations, a carcass ply (impregnated cord in a layerof rubber mix) is applied. There therefore results a thin intermediatelayer of mix of lower modulus which is located between the mix of highmodulus and the portion of reinforcement structure. With direct contact,i.e., without the presence of this thin layer of mix of lower modulus,the impact of the presence of the mix of high modulus in the zone 40 ais amplified. In fact, the traditional thin layer of lower moduluscauses loss of energy, which may cause deterioration of the mechanicalproperties.

By modifying the thickness of the zone 40 a and/or by using a mix with amore or less high modulus, a tire with the desired rigidity, suited forthe intended use, can be obtained. This example is well-suited to tiresof the passenger-car, van or light-truck and two-wheeler types.

FIG. 10 shows a variant in which the arrangement 30 of secondary cords31 is arranged in a zone comprising different sub-zones each havingdistinct mechanical properties, in particular different elasticitymoduli.

For example, the zone 42 is of high modulus (such as, for example,greater than 12 MPa), the zone 60 is of very high modulus (such as, forexample, greater than or equal to 25 MPa), and the zone 50 is of lowermodulus (such as, for example, less than or equal to 12 MPa).

By thus refining the distribution of the zones, it is possible tooptimize the characteristics of the bead 1 by taking into account thedifferent demands for each of the zones; for example, maximum hardnessand rigidity at the base of the bead, then greater flexibility from therim hook onwards.

Starting from these few examples, other arrangements may be proposed,for example, one variant having simultaneously the zones of high modulusof FIGS. 9 and 10.

FIGS. 11 and 12 illustrate examples of another embodiment of a tireaccording to the invention. In this embodiment, on either side of thereinforcement structure 10 there are arrangements 20 of main cords 21 ofdifferent diameters. According to the invention, the arrangement of thecords of the arrangements 20 is such that the surface density of themain cords 21 arranged on the axially inner side 3 relative to thestructure 10 is greater than the surface density of the main cords 21arranged on the axially outer side 2 relative to the structure 10. Inthe example of FIG. 12, this latter criterion is met even if the numberof main cords 21 on the axially inner side 3 is less than the number ofmain cords 21 of the axially outer side 2. According to an advantageousexample, the surface density corresponds to the total of the surfaces ofthe cord profiles (cut cords or filaments or cables or plied yams). Forexample, a restricted number of cords of large diameter may occupy alarger surface than a larger number of cords or cables or filaments ortwisted yams, etc, of generally smaller diameters. The total of thesurfaces is important: it may be a total of identical or non-identicalsurfaces.

In the different examples described and illustrated, there is at leastone arrangement of cords along a substantially circumferential patharranged substantially adjacent to the reinforcement structure, thearrangement of the cords of said arrangements being such thatΣ(E_(I)×S_(I))_(int)>Σ(E_(e)×S_(e))_(ext), in which E_(I) and S_(I)represent respectively the Young's modulus and the surface of each cordarranged on the axially inner side relative to said structure, and inwhich E_(e) and S_(e) represent respectively the Young's modulus and thesurface of each cord arranged on the axially outer surface relative tosaid reinforcement structure. The total of the products of the moduliand the effective surfaces of each of the cords on either side of thereinforcement structure constitutes a reliable, accurate measurement andcomparison parameter. Advantageously, this formulation furthermore makesit possible to take into account in the comparison any type of cord orfilament or cable. Preferably the comparison is effected from cordsarranged in the zone of the bead or in the anchoring zone of thereinforcement structure in the bead.

1. A tire, comprising at least one reinforcement structure anchored oneither side of the tire in a bead, the base of which bead is intended tobe mounted on a rim seat of a standard rim for the tire, each bead beingextended radially towards the outside by a sidewall and comprising anaxial bearing zone extending substantially between the base of the beadand a radial position of the bead substantially corresponding to theposition of the radially outer edge of a hook of the rim, the sidewallsradially towards the outside joining a tread, on the circumference ofthe tire the at least one reinforcement structure extending from an endportion of the structure, arranged in the bead, towards the sidewall, atleast one arrangement of main cord windings along a substantiallycircumferential path being arranged substantially adjacent to the endportion so as to form an anchoring zone, the main cord windingsanchoring the at least one reinforcement structure in the bead and/orclamping the bead, wherein a number of main cord windings arranged onthe axially inner side relative to said at least one reinforcementstructure is greater than zero, and a number of main cord windingsarranged on the axially outer side relative to said at least onereinforcement structure is equal to or greater than zero, thearrangement of the cord windings of the at least one arrangement beingsuch that the number of main cord windings arranged on the axially innerside relative to the at least one structure is greater than the numberof main cord windings arranged on the axially outer side relative to theat least one structure, all of the main cord windings having a radialposition not extending beyond the axial bearing zone.
 2. A tireaccording to claim 1, in which all of the arrangements of main cordwindings are on the axially inner side relative to the at least onestructure.
 3. A tire according to claim 1 wherein the at least onearrangement of main cord windings includes an arrangement of main cordwindings on the axially inner side of the at least one reinforcementstructure and an arrangement of main cord windings on the axially outerside of the at least one reinforcement structure, the tire furtherincluding at least one arrangement of secondary cord windings which arearranged axially to the outside relative to the at least onereinforcement structure.
 4. A tire according to claim 3, in which thesecondary cords are non-metallic.
 5. A tire according to claim 3, inwhich the main cords have a high elasticity modulus.
 6. A tire accordingto claim 3, in which the at least one arrangement of secondary cordwindings is arranged so as to be in contact with at least one rubber mixof high modulus.
 7. A tire according to claim 1, in which at least oneportion of the main cord windings and the structure portion in theimmediate vicinity of the cord windings are embedded in a rubber mix ofa modulus greater than 25 MPa.
 8. A tire according to claim 7, in whichthe modulus is greater than 40 MPa.
 9. A tire according to of claim 1,in which the at least one reinforcement structure comprises, at thelevel of the bead, at least two structure portions, with theinterposition of an arrangement of cord windings between at least two ofthe adjacent portions.
 10. A tire according to claim 1, in which the atleast one arrangement of cord windings is surrounded on one side by afirst rubber mix and on the other side by a second rubber mix which isdifferent from the first mix.
 11. A tire according to claim 1, in whichthe end portion of the at least one structure has a substantially radialmeridian profile.
 12. The tire of claim 1, in which the number of maincord windings arranged in the axially inner side is at least 1.5 timesgreater than the number of main cord windings arranged in the axiallyouter side.